A Different Transmission Fault

[TerryO]

Hi all,

Lately I keep getting a dash warning popping up saying Transmission Fault.

When it does this the Sports mode / manual shift becomes inactive. When I try and read the faults with my Hawkeye nothing comes up as a read fault. However if I hit the clear button then the Transmission will work properly for a while, until the fault once again pops up on the dash.

Other than that the auto seems to be working fine, I had the fluid changed 40k ago and had a steel pan fitted and will be getting a double flush done soon.

Any ideas?

[~Rich~]

Make sure all your software is up to date is the first thing I'd try.

[TerryO]

Thanks Rich,

All the software was updated just over a year ago, including transmission and transfer case software.

cheers,
Terry

[Rich84]

Terry, I've had the same fault pop up twice in a month. Exactly the same symptoms as you:
-Transmission Fault message on dash.
-Selecting sport mode or manual mode doesn't do anything.
-The torque converter clutch stops locking up and revs go all over the place in all gears. Acceleration is generally much slower without the lockup clutch! Does yours do this?

Both times this has happened going up a steep rutted hill, one time towing a trailer.

Hasn't reappeared in any other situations. I was going to do a full trans flush with steel pan and also an auxiliary cooler in place of the radiator cooler.

[Tote]

Could be taillight bulbs, the couple of times I've had similar faults one of the tail light bulbs has blown a few days later.

Regards,
Tote

[Geedublya]

Mine is giving similar faults randomly usually accompanied by HDC and parking brake errors. I suspect the canbus and the connection to the transmission ECU especially since the last time it occurred after I washed it. I'm going to clean the connector to the transmission ECU.

[TerryO]

I noticed a park brake error pop up last time as well. It does seem to happen more often then not on bumpy roads which I guess suggests something is loose. I checked and none of the bulbs are blown.

I would imagine it is not related but the fuel gauge is now very unreliable and is randomly reading all over the place, to the point I ran out of fuel on Monday in the middle of no where and had to get towed home.

[Geedublya]

My fuel gauge generally reads OK, though sometimes it reads 7/8 full when it isn't. I ran out on Tuesday (reading 7/8 full) when I forgot I had reset my trip meter and subsequently didn't top up the main tank from the auxiliary.
I always reset my trip meter when I fill up and generally top up the main tank at 500km and refill both tanks before 1200km.

Bleeding the fuel system is a pain when the fuel is hot :(.

As far as I can tell the fuel gauge and the transmission problems are separate.

From what I have found reading on various forums the connection to the transmission ECU is susceptible to corrosion and can give the errors we are seeing. This was the reason they moved the ECU to the 2nd battery tray on the D4.
I am away again this weekend so won't get to look at it until the next. I'll report what I find.

[TerryO]

That is exactly what my fuel gauge started doing a couple of months ago and come to think of it it was about the same time the auto error light starting popping up.

So it might be a just a coincidence that we both have the same issues or maybe they are related?

[Geedublya]

Fuel gauge has been acting up for more than a year, transmission faults just started occurring.
I suspect that one of the tank sensors is either dirty or the carbon resistor is worn.

[Graeme]

This was the reason they moved the ECU to the 2nd battery tray on the D4.That ecu is not the transmission ecu, it is the transfer case ecu. However in the 2nd battery tray is the loom connection between the gearshift lever mechanism and the gearbox itself.

[Geedublya]

You are correct Graeme, I'm getting my ECUs mixed up. What I should have written is that the CAN connections to the Transfer case ECU are prone to getting wet and corrosion can occur.

The detail below is from the manual. I have seen problems with ones in red. I usually see transmission fault, HDC unavailable, Park brake faults and sometimes suspension faults. I suspect if I try to select low range I would get an error as well.

CONTROLLER AREA NETWORK (CAN)
The high speed CAN broadcast bus network is used to connect the powertrain modules. The CAN bus is connected
between the following electronic units:
High Speed CAN Bus
�� TCM (Transmission Control Module)
�� Instrument cluster
�� Air suspension module
�� Steering angle sensor
�� Rear differential module
�� Centre console switch pack
�� Electric park brake module
�� Restraints control module
�� Engine Control Module (ECM)
�� ABS control module (HDC faults)
�� Adaptive front lighting control module
�� Transfer box control module
�� Adaptive cruise control module
�� Diagnostic socket.
The CAN bus allows a fast exchange of data between modules. The CAN bus comprises two wires which are identified as
CAN high (H) and CAN low (L). The two wires are coloured yellow/black (H) and yellow/brown (L) and are twisted
together to minimise electromagnetic interference (noise) produced by the CAN bus messages. For additional information,
refer to Communications Network (418-00 )
In the event of CAN bus failure, the following symptoms may be observed:
�� Transmission operates in default mode
�� Torque converter lock-up clutch control is disabled
�� Gear position indication in instrument cluster message centre inoperative (this will also occur with any
transmission fault).

[Graeme]

The TC module and its connector not being sealed is a weak point in the general water-proof connections everywhere else where water can reasonably be expected to get. The suspension ecu's connectors aren't sealed either but water doesn't usually get inside the cabin.

[Rich84]

You are correct Graeme, I'm getting my ECUs mixed up. What I should have written is that the CAN connections to the Transfer case ECU are prone to getting wet and corrosion can occur.

In the event of CAN bus failure, the following symptoms may be observed:
�� Transmission operates in default mode
�� Torque converter lock-up clutch control is disabled
�� Gear position indication in instrument cluster message centre inoperative (this will also occur with any
transmission fault).

This is the exact fault I am getting. Has happened twice, the last time was two weeks ago. Whereabouts is the TC ECU on these cars? Near the battery? What should I be looking for?

[Graeme]

Rich, those faults might only involve the gearbox wiring, not necessarily the HS canbus or any other ecu connected to it. Anyway, the transfer case module in the D4 is located forward of the brake booster and I understand the D3's is in the same place.

[Geedublya]

D3 is mounted behind the battery from what I understand.

Yes, if you are only getting one fault it is probably the gearbox or connection to it.

[Geedublya]

Today after replacing the alternator I finally got around to checking the transfer case ECU connectors.
On the D3 it is located behind the battery inside a plastic compartment.
http://s55.photobucket.com/user/geedublya/media/Cars/P1010005.jpg.html
http://s55.photobucket.com/user/geedublya/media/Cars/P1010013.jpg.html

Someone had been there previously and broken the clips that hold the compartment together. Mine was held together with duct tape.
The compartment is sealed however I wouldn't like to submerge it. It should be splashproof in normal circumstances though.

The ECU unclips from the compartment and then you just remove the connectors. I found corrosion and evidence of water ingress on the middle connector.
http://s55.photobucket.com/user/geedublya/media/Cars/P1010001.jpg.html

I cleaned both the plug and socket with a toothbrush and contact cleaner, I used a product called deoxit (http://store.caig.com/s.nl/sc.2/category.188/.f). On reassembly I used Dow Corning DC4 (http://www.dowcorning.com/applications/search/products/details.aspx?prod=01903128&type=prod) electrical compound on the connectors hopefully this will prevent more corrosion and water ingress in the future. Of course I will order a new compartment as well.

So far there have been no errors I'll see how it goes over the next few weeks.